Question

Consider the four diagrams below where in each case, HA is an acid and is represented by 60, H is a hydrogen ion and is represented by , A is an anion and is represented by and water molecules are represented by . 1. Which diagram represents a relatively concentrated, weak acid? Explain. 2. Which diagram represents a relatively concentrated, strong acid? Explain. 3. Assign relative strengths and concentrations to the two remaining diagrams. Explain.

Answer 1

oo represents HA, o represents H+ and o represents A-.

How to differentiate between weak and strong acids?

Strong acids dissociate (ionize) completely in water, whereas weak acids do not dissociate completely in water. So a solution where we find only o and o (only dissociated ions) is a solution of strong acid whereas for a weak acid solution, we will find both dissociated ions (o and o) as well the undissociated acid molecule oo.

How to differentiate between concentrated and dilute acid?

A concentrated solution is the one where the amount of acid will be more compared to that of water (the solvent), and a dilute solution is the one where the amount of acid will be less compared to that of water. So the solution where we find few H2O molecules (compared to the number of acid molecules or ions) is a concentrated solution, and the solution where we find a lot of H2O molecules is a dilute solution.

1. Diagram B represents a relatively concentrated weak acid.

It is weak acid because there are both dissociated ions and undissociated acid molecule. It is concentrated because there are comparatively less H2O molecules than the acid molecules.

2. Diagram C represents a relatively concentrated strong acid.

It is strong acid because there are only dissociated ions in the solution. It is concentrated because there are comparatively less H2O molecules than the acid molecules.

3. In diagram A, both dissociated ions and undissociated acid molecules are present. So it is a weak acid. Also there are lots of H2​​​​​​​O molecules compared to the acid molecules. So Diagram A represents a relatively dilute weak acid.

In diagram D, only dissociated ions molecules are present. So it is a strong acid. Also there are lots of H2​​​​​​​O molecules compared to the ions. So Diagram D represents a relatively dilute strong acid.